1. Field of the Invention
This invention relates generally to electrical computers and data processing systems and more particularly to apparatus for selectively executing program instructions out of the normal sequential order.
2. Background Description
In high performance computer apparatus such as, for example, scientific processors and some general purpose machines, instructions are normally accomplished in the order specified by a program. Normally, these instructions are both executed and finished sequentially in program order. To increase performance and limit delays, some machines have been improved to accomplish the finishing of program instructions out of order so as to overlap with execution instructions. However, the execution instructions are limited to the sequential order called for by the program. A general requirement of such program instruction overlap is that the instructions are completed as though they had been accomplished in the order specified by the program. Program instruction overlap is desirable to increase performance but may involve machine complexity and increase hardware cost. It would be beneficial to further improve program instruction overlap to accomplish both execution and finishing of program instructions out of order without undue complexity and prohibitive cost.
The foregoing illustrates limitations known to exist in present devices. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.